It has hitherto been a general practice for a precision bearing for a machine tool that the bearing is allowed a rust preventive oil to be applied after the cleansing of the bearing, then wrapped with a film-like vinyl sheet and finally packaged in a box made of, for example, cardboard. When the bearing is ready to be used, it is necessary to remove the rust preventive oil applied to the bearing and, therefore, the bearing must be cleansed.
In the practice of the method of lubricating the precision bearing of a kind used in supporting the machine tool spindle, an extremely small quantity of lubricant oil such as an air oil lubricant (oil and air lubrication) or an oil mist lubricant is supplied. If the rust preventive oil remains unremoved from the bearing, the lubricating performance will be adversely affected, and therefore a problem will arise that heat may evolve in the bearing. For this reason, the rust preventive oil is necessarily required to be cleansed.
There has been also suggested a method of storing a bearing, in which the bearing is sealed within a gas barrier bag with a rust inhibiting bag of a kind, in which a composition containing an unsaturated chlorinated aliphatic compound and a catalyst is wrapped with a gas permeable packaging material. (See, for example, the Patent Document 2.)
As a rust preventive packaging method for a general merchandise, a rust preventive packaging method has been suggested, in which the merchandise is packaged in a usual polyethylene bag together with a rust preventive polyethylene sheet impregnated with a vaporizable rust preventive agent. (See, for example, the Patent Document 3.)                Patent Document 1: Japanese Laid-open Patent Publication No. 2003-176832        Patent Document 2: Japanese Patent No. 3028966        Patent Document 3: Japanese Laid-open Patent Publication No. 2003-312748        
In the conventional method in which the rust preventive oil is applied to the bearing, since the cleansing of the bearing is required in order to remove the rust preventive oil, problems have been recognized that the use of a cleaning apparatus is necessary, control of dusts and grit contained in a cleansing liquid is required, disposal management of the cleansing oil is also required, a substantial length of time is required to accomplish the cleaning, and the workability is extremely low. In particular, the problems associated with the use of the cleansing oil and waste oil are cumbersome in recent years in the face of improvement in the working environment and reduction of environmental loading and, therefore, it is generally felt that the cleansing oil should not be used.
Also, considering that the bearing for the support of the machine tool spindle is used in a high speed environment, increase of the lubricating performance is keenly necessary. In addition, where the cleansing process such as described hereinabove is required in the site of a customer such as, for example, a machine tool manufacturer, there may be a problem in that control of the cleansing level will affect the lubricating performance.
In view of the foregoing, if the bearing were to be used without being cleansed and in the form readily used as removed from the package, the foregoing problems would no longer be moot and the bearing would be a environmentally friendly product.
The method, in which the bearing is sealed within the gas barrier bag together with the rust preventive bag requires the concurrent use of the rust preventive bag and is therefore time-consuming and, if one fails to enclose the rust preventive bag within the gas barrier bag, no rust preventive property will be available.